1. Field of the Invention
The present invention generally relates to a method of allocating, in a base station apparatus, radio resources for a link between the base station apparatus and a mobile station apparatus, and further relates to the base station apparatus.
2. Description of the Related Art
In audio communication of mobile communications systems, an uplink for carrying audio from a mobile station has traffic substantially the same amount as that of a downlink for transmitting audio to the mobile station. Radios resources such as frequency bands used in the frequency domain duplex (FDD) method or time slots used in the time domain duplex (TDD) method are thus allocated to the uplink and the downlink symmetrically.
In recent years, the proportion of non-audio communication has been on the increase in the mobile communications. It is expected that multi-media services will further develop, providing users with various information services, exchange of email, applications for transmitting information from a user end, etc.
When information traffic of such services and applications is taken into consideration, data delivery from databases accounts for a large proportion of information traffic in the case of information service, so that downlink has a large amount of traffic in the network and radio channels. In the case of information transmission from a user end, on the other hand, an uplink has a heavy traffic. In this manner, non-audio communication such as data and image communication is believed to need an uplink and a downlink that are asymmetric in terms of traffic.
Further, there may be abundant cases in which traffic characteristics differ between an uplink and a downlink depending on the hours. For example, a large number of Web accesses may be made during lunchtime or at night, resulting in an increase of downlink traffic. During the daytime except for lunchtime, a large amount of traffic are used for audio communication and email exchange, so that the traffic of uplinks and downlinks are expected to be more symmetrical compared to during lunchtime or at night. Further, there will be a time when uplink traffic shows a great surge for a certain time period such as in the case of ticket bookings.
If radio resources are symmetrically allocated to a downlink and an uplink as in the case of conventional audio communications despite actual asymmetric traffics between the uplink and the downlink, there will be excess resources in one link if the allocation is made to match the greater one of the two traffics, or there will be a shortage of resources in one link if the allocation is made to match the smaller one of the two traffics. In this manner, efficient information transfer cannot be made, resulting in a decrease of user satisfaction.
In the FDD method, for example, frequency bands of an uplink and a downlink are fixed to an identical bandwidth, so that uplink traffic and downlink traffic cannot be made asymmetrical. In the TDD method, there is a technique that changes the boundaries of uplink slots and downlink slots in response to a ratio between the uplink traffic and the downlink traffic that are generated at a particular instant. This technique is lacking in stability, and ends up providing a reduction in usage efficiency if it cannot closely follow the traffic changes.
Accordingly, there is a need for a method of allocating radio resources and a base station apparatus using such a method where the method is efficient, flexible, and stable.